Forest Openings and Pollinators Too
by Scott Johnson, RGS & AWS Forest Conservation Coordinator – Minnesota & NW Wisconsin
We RGS & AWS members talk a lot about the size, species and spacing of trees. We talk about how historical disturbances of wind and fire maintained a shifting mosaic of forest characteristics, providing that ideal mix of young, dense forests so important for brood rearing habitat for ruffed grouse and American woodcock, and older forests that are imperative for ruffed grouse winter habitat needs, as well as for future young forests.
We talk about how valuable it is to use those natural disturbance histories and conditions to guide our modern management of forests. We know that management that encourages a mix of forest ages, as well as a mix of appropriate tree species across the landscape, will best provide for the habitat needs for many wildlife species, as well as for general forest health, an extensive list of ecosystem services and a sustainable source of forest products. Many of our forest ecosystems in ruffed grouse and American woodcock range also historically included patches of short- and long-term open conditions. Areas of thin, dry or seasonally wet, saturated soils, along with wind, fire and flooding disturbance, maintained these gaps in the forest canopy.
These areas provided patches of another type of vegetation diversity, with a variety of low, flowering herbaceous plants and grasses. We know these openings are important for American woodcock singing and roosting locations, and can be great sources of insects for growing ruffed grouse chicks as well.
Openings in the Forest Canopy
Because of these openings’ open conditions, they provide increased sunlight and greater visibility compared to the adjoining forest. This results in greater herbaceous vegetation production and early spring green-up, valuable for many wildlife species as an early season food source as well as insect production, which in turn provides a critical food source for developing ruffed grouse chicks — along with many other forest birds. The open visibility is used by wildlife for breeding displays such as woodcock singing grounds as well as for their nighttime roosting areas. In the years immediately following wildfires or timber harvest, before tree regrowth dominates the area, log landings, skid trails, roadsides, gravel pits, pastures and old fields often create openings in the forest canopy suitable for these wildlife needs.
Land managers interested in providing these habitat benefits to ruffed grouse and American woodcock, as well as white-tailed deer, black bears and many other wildlife species also often deliberately clear and maintain scattered forest openings. For American woodcock and ruffed grouse, it’s important to locate these openings in close proximity to young, dense forest, brood-rearing cover and in landscapes otherwise dominated by forest cover. Taking advantage of and developing or expanding existing openings such as log landings can be an efficient way to provide wildlife openings.
Multi-use land management objectives can also be incorporated with maintained forest openings, as these may provide “ready” locations for new logging access routes and landing areas, as well as great hunting, wildlife watching and other outdoor activities. The ideal number of openings, and their size and distribution, depend on many possible management goals, as well as on the local forest ecology and the surrounding landscape. For example, creating additional openings in a small forest stand within an otherwise open agricultural landscape may not bring much benefit to ruffed grouse or American woodcock. However, 1/2- to 5-acre openings scattered across an otherwise forested landscape will likely be valuable, and ruffed grouse and American woodcock will often use them. Maintaining these openings through periodic disturbance and promoting desirable plant cover and density within them is equally important.
Enhancing Forest Openings for Pollinators
While almost any opening in the forest canopy will increase sunlight hitting the ground and provide some benefits to wildlife, promoting a diversity of native flowering plants may make them even more valuable. Many forest openings were originally seeded with nonnative vegetation, or just a single herbaceous species. Others have been totally invaded by other undesirable nonnative species such as spotted knapweed. Often such openings are overly simple, with only a few plant species present.
Many populations of pollinating insects are in decline, and several individual species, including the well-known monarch butterfly and native bees, have been identified as urgently needing special consideration. Obviously, flowering plant pollination is critical to healthy forest ecosystems and all living things. Just as with management for healthy forests and abundant wildlife, adequate habitat diversity is needed to improve conditions for pollinators. A variety of native plants that flower at different times throughout the growing season has been found to be the best way to provide for pollinators.
On prairie landscapes, it seems that land managers have been ahead of those of us in the forest lands in terms of enhancing habitat for pollinators by reestablishing diverse native flowering herbaceous plants. Within many of the forest openings we’ve discussed – whether naturally occurring or deliberately or incidentally created – there’s clearly an opportunity to benefit pollinators and improve insect availability to ruffed grouse broods and other forest birds at the same time. Following disturbances in forest openings, a common practice has been to reseed with cheap, readily available and easy-to-establish plants such as clover and timothy grass to rapidly revegetate and stabilize exposed soils, hold off unwanted invasive weeds and provide some of the wildlife benefits we’ve been discussing. No doubt these seedings have been valuable too, and in some circumstances are still the best option.
I myself have seeded many disturbed soil areas with clover and have seen soils rapidly stabilized and have happily seen the wildlife respond! Compared to a typical pollinator planting, though, where a variety of native plants that will flower throughout the growing season are used, such openings are not very diverse. While simpler openings will still provide many important wildlife habitat benefits, enhancement of forest openings by reestablishing diverse native flowering plants will do the same and provide for pollinator insects.
Establishing native flowering plants will cost more and take longer to establish than some nonnatives. However, many natural resources agencies, consultants and private seed companies are realizing this important opportunity to provide for pollinators and are finding solutions appropriate for our forest ecosystems While many of the clovers and timothy grass seed sources are grown with refined and efficient production systems, many native plants are not yet compatible with mechanized seed collection or production growing. Also, they inherently require more diverse site preparation techniques before seeding or planting.
Since many of these desirable native plants have a growth strategy of putting early energy into their roots, they are often susceptible to faster-growing nonnatives and may be outcompeted or even taken over by aggressive invasive weeds. While I regularly broadcast seeded clover into just slightly disturbed soil with great establishment success and probably recruited some already present native “volunteers,” most native flowering plants will require more intensive soil preparation [Figure 6 about here] with treatments such as herbicide application, prescribed burning and soil tilling, as well as drilling seed and subsequent maintenance weeding, burning or mowing.
A note here: Forest openings are not naturally uniform, and wildlife using them don’t necessarily benefit from them being manicured perfectly. Some diversity within these openings, such as scattered encroaching brush and/or patches of very low-density flowering plants, provide “feathered” habitat preferred by many wildlife species. Knowledge of appropriate and wildlife-valuable native pollinator species and methods for establishing and maintaining them in forest openings is thankfully improving and may be an option for a wildlife forest opening of yours! We know forest openings are natural and important parts of forest ecosystems. Some areas may already have adequate openings in the forest, while in others it may be worth considering creating or expanding them. They can provide improved habitat conditions for ruffed grouse and American woodcock and a host of other important forest wildlife species and can be compatible with multiple-use forest management goals. When we include openings in our forest management plans, it may be worth considering enhancing their value for pollinator insects by establishing a diversity of native flowering plants, too.
